EVOH resin has a high crystallinity due to firmly hydrogen bonding between hydroxyl groups in the polymer chain thereof, therefore exhibiting strong intermolecular force. Not only crystal part but also amorphous part in EVOH resin can exhibit strong intermolecular force. This provides EVOH resin film with excellent gas-barrier property.
EVOH resin is utilized for packaging film or sheet, or container such as bottle for food, pharmaceutical, industrial medicine, agricultural chemicals, and so on, because of the excellent gas-barrier property.
On the other hand, EVOH resin is brittle and lacks flexibility, which is defect of EVOH resin. In the case that a packaging or molded article as a final product of EVOH resin is subjected to repeated folding, the defect is liable to crack or generate pinhole due to flex fatigue and makes difficult to retain the excellent gas barrier property of EVOH resin.
In order to solve these problems, for example, JP S63-230757A (Patent document 1) suggests a resin composition employing a combination of two EVOH resins differing in content of ethylene unit (hereinafter, “ethylene unit content”) and satisfying a specific relation in solubility parameters of these EVOH resins.
It is generally known that the lower ethylene unit content the EVOH resin has, the more excellent gas-barrier the EVOH resin exhibits. Also it is known that the higher ethylene unit content the EVOH resin has, the more increased strength the molded article by hot-drawing has. These make possible to keep gas-barrier property at the same time hot-drawing moldability secures by combining an EVOH resin having a relatively high ethylene unit content together with an EVOH resin having a relatively low ethylene unit content.
By the way, a film of EVOH resin and a multilayer structure including an EVOH resin film. (EVOH resin layer) are commonly produced by feeding pellets of EVOH resin to an extruder and melt-molding into film or sheet. Thus produced film or sheet of EVOH resin and a multilayer structure including EVOH resin film or sheet are formed to a container by fabrication with a mold such as deep drawing or air-pressure forming.
The patent document 1 discloses that pellets produces by pelletizing after dry-blending two types of EVOH resins with extruder or the like are used as a molding material. According to the patent document 1, if EVOH resins are unevenly dry-blended in the pellet production, thus produced pellets are likely to provide a nonuniform EVOH resin layer or EVOH resin layer with torn.
Precision of shape or thickness of a molded product varies depending on properties of EVOH resin pellets used as a molding material. For this reason, a molded product sometimes does not exhibit properties expected from intrinsic properties of EVOH resin used as a molded material.
Pellets capable of obtaining a molded article with desired properties based on intrinsic properties of EVOH resin are suggested in, for examples JP2000-264972A (Patent document 2). The patent document 2 discloses that if angle of repose of EVOH resin pellets is adjusted to the range between 30 and 45° by addition of 10 to 1000 ppm of lubricant to EVOH resin, the EVOH resin pellets exhibit excellent feed property to an extruder in melt-extrusion molding as well as reduced variation in torque and discharge of the extruder in molding. As a result, a molded article having precision of shape and dimension such as thickness may be obtained.